Abstract: An offshore structure for deepsea production of this invention is designed for achieving economy both in installation and in operation. It consists mainly of a base to be founded on a sea-bed, a buoyant body having a separator segregated from the sea for storing and separating the produced fluids and an elongate tensioned member for connecting the base and the buoyant body and transporting the produced fluids from the well through the base to the separator near the surface of the sea. The separator has a compartmentalized outer wall for controllably variable ballasting and deballasting.

Abstract: A multi-well hydrocarbon development system is economically established and operated by drilling cluster wells through the piles securing the base structure which supports a semisubmersible tension leg buoy through a single leg assembly. The buoy includes a turntable with skid beams on which a drilling rig is slidably mounted so that the rig can be positioned over the piles and cluster wells can be drilled through the piles. Produced fluids are transported into a containment means for separation and storage within the buoy. A captive processing vessel may be moored to the buoy and a means is provided to dispose processed water and/or gas responsibly.